I. Field of the Invention
The invention relates generally to a method for repairing glass panes and more particularly, to such a method which permits repair of the pane without removal of the pane from its support structure.
II. Description of the Prior Art
It is well known that glass is a brittle material and is quite susceptible to fracturing upon impact with another object. Fractures of the glass panes often result in sharp edges which can be very dangerous. Moreover, once a pane has been fractured, portions of the pane may become dislodged from the main body of the pane which results in a weakened pane structure susceptible to breakage from very slight forces or stresses. In addition, once a crack has been started in a pane of glass, forces and stresses which would not have been strong enough to originally fracture the glass can cause the cracks to lengthen throughout the body of the pane. Since replacement of the entire pane is extremely costly, it would be advantageous to be able to effectively repair and secure fractured portions of a pane so that replacement of the pane is not necessary.
In order to effectively repair the pane of glass, it is first necessary to eliminate points of stress within the pane. For instance, an incomplete crack in a pane of glass cannot be effectively repaired by merely applying glue or other adhesive within the crack since the end of the crack is a point of high stress and the crack can easily be continued by relatively light stresses or forces exerted upon the pane even though the original portion of the crack has been glued. It has been found that a stress point such as that at the end of a crack can be eliminated by cutting a smooth hole around the end of the crack to eliminate rough edges which become points of maximum stress.
The previously-known devices for cutting holes in panes of glass generally utilize annular core drills having a coating of diamond bits secured thereto. Such core drills are often manually urged against one side of the glass pane in order to cut therethrough. Such manually applied forces is often inconstant and thus results in a hole having various stress points around its periphery. Moreover, such inconsistent force causes excessive wear of the diamond bit coating since the abrasion of the core drill against the glass causes diamond bits to break off from the core drill body. Since the cutting blade portion of the core drill wears rapidly, it is necessary to provide a cutting blade portion which is sufficiently long to enable the core drill to be used repeatedly. Since the cutting blade portion is made of diamond bits, the cost of each core drill is relatively high. Thus, it would be advantageous to prolong the wear of the cutting blade portion in order to make the cutting operation more economical.
Another previously-known drilling device disclosed in U.S. Pat. No. 4,073,094 for use on glass panes provides a pair of core drills which are placed on opposite sides of the pane of glass and then simultaneously rotated in one direction while being urged toward each other. A single spring means urges the core drills toward each other. This previously-known device is disadvantageous in that since the axial force applied to each core drill is not separately adjustable, the core drills will abut against each other only at one point within the pane of glass. Thus, when the cutting edge of each core drill becomes slightly worn and rounded, a small ridge will be formed around the periphery of the hole at the point at which the core drills abut against each other. Moreover, since the disclosure of that patent teaches the use of core drills having different diameters, a stepped hole results. Thus, once the core drills abut against each other at a point within the pane, the core drill assembly cannot be axially shifted back and forth to ream out ridges occurring within the drilled hole. In addition, the edge of the step formed within the hole is a point of high stress and, therefore, very susceptible to breakage.
Once a hole has been drilled, it is typical to insert a glass plug and align it within the pane so that it is relatively unnoticeable. Moreover, if the plug is not accurately aligned within the hole, it is difficult to apply epoxy or another adhesive around the plug to provide secure engagement of the plug around its entire periphery within the pane. Thus, it would be advantageous to provide a method which accurately aligns the plug while it is installed so that the entire space around the plug within the hole can be filled with securing agents such as epoxy.
Oftentimes it is disadvantageous to use a core drill to relieve the stress area in the pane of glass since they remove a relatively large area of glass around the fracture. Thus, when only a small hole is to be repaired in the glass, it would be advantageous to remove only a small portion of the glass around the small hole in order to relieve the stress. In addition, the use of a core drill to relieve stress at the end of a crack in a glass pane is disadvantageous because the rotational force of the core drills increases the stress exerted upon the pane and can cause the crack to lengthen. Thus, it would be advantageous to remove such stress points from the pane without exerting torsional stresses incident to the core drilling.
Moreover, when a small hole is to be repaired, it is difficult to effectively secure a plug within the hole. Previously-known cylindrical plugs can be easily dislodged from the pane. Therefore, it would be advantageous to provide a method for forming a plug which lockingly engages the pane of glass, so that the plug cannot be removed from either side of the glass yet which is still mounted flush to the sides of the pane of glass.
It has previously been extremely difficult if not impossible to effectively repair a laminated windshield without delaminating a large portion of the pane. Thus, it is extremely expensive to repair laminated windshields by previously-known methods. Moreover, the difficulty and expense of such an operation often necessitated replacement of the entire laminated pane or windshield.